"We needed to be more confident in attack," Nani told UEFA's official website.
"We were not too good in between the lines and we didn't believe enough that we could harm our opponent. We were calm before the goal and, after that moment, it became more difficult to overturn the result.
"We have plenty of matches ahead of us and we have to win them all. We need to develop our mentality and grow up as a team and individuals and we have to believe that we'll manage to win the games to come."
Nani is currently on loan at former club Sporting Lisbon from Manchester United.